If you're eating only healthy food then it could be that your portion sizes are causing you to gain weight. Or the food you think is healthy is really quite high in fat or calories (I used to love light coconut milk in curries until I found out just how non-light it really is!)
A lot of people here swear by CalorieKing.com.au (http://www.calorieking.com.au
) for their weight loss. It's great because when you set up an account you enter your current weight and activity level and your target weight. That way it can tailor your program to how many calories you need to lose weight. It's a great way to educate yourself about how many calories and grams of fat food contains and even if you decide to try another method of weight loss the knowledge helps a lot. CalorieKing.com.au suggests 60 minutes of exercise per day. You can enter in your exercise activities and it will subtract those calories burned from your calories consumed to make sure you keep within a healthy range of calories.
60 minutes of moderate intensity exercise would be good for weight loss, but don't try too much too soon. If you are unused to physical activity start with 15 minute walks and gradually extend them to 30 minutes. You don't have to do all of those 60 minutes exercise at once. If it's easier to fit in 10 minute sessions into your schedule then give that a go to start off with.
There is a lot of exercise information available at SparkPeople.com (http://www.sparkpeople.com
) and if you sign up for their newsletter you'll get them in your email inbox daily. They also have diet plans there, but I find CalorieKing is better because it has more Australian food in its database. SparkPeople concentrates only on food available in the US.